Method for making microstructures and photolithography mask plate

ABSTRACT

A method of making microstructures, including: setting a photoresist layer on a base; covering the photoresist layer with a photolithography mask plate, wherein the photolithography mask plate includes: a substrate; a carbon nanotube layer on the substrate; a patterned chrome layer on the carbon nanotube layer so that the carbon nanotube layer is sandwiched between the patterned chrome layer and the substrate, wherein a first pattern of the patterned chrome layer is the same as a second pattern of the carbon nanotube layer; a cover layer on the patterned chrome layer; exposing the photoresist layer to form an exposed photoresist layer by irradiating the photoresist layer through the photolithography mask plate with ultraviolet light; and developing the exposed photoresist layer to obtain a patterned photoresist microstructures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/684350, filed on Aug. 23, 2017, entitled,“PHOTOLITHOGRAPHY MASK PLATE”, which claims all benefits accruing under35 U.S.C. § 119 from China Patent Application No. 201611095319.2, filedon Dec. 1, 2016, in the China National Intellectual PropertyAdministration, the contents of which are hereby incorporated byreference. The disclosures of the above-identified applications areincorporated herein by reference.

FIELD

The subject matter herein generally relates to a photolithography maskplate.

BACKGROUND

At present, with in depth studies on microstructures, microstructurescan be applied to multiple fields, such as special surfaces of opticaldevices, hydrophobic material, anti-reflection surfaces. For example, amicrostructure is generally provided in a light guide plate in order toimprove the light emission efficiency in the optical devices. The mainmethods for making the microstructures are photolithography, etching andso on. Photolithography is widely used because of the simple process,easy operation and preparation in a large area. However, the maskmaterial in photolithography are generally plastic, glass or patternmetal. The microstructures obtained by these mask material have lowdimensional accuracy. Also it is difficult to obtain microstructures innanoscale.

What is needed, therefore, is to provide a photolithography mask platefor solving the problem discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views. Implementations of the present technologywill now be described, by way of example only, with reference to theattached figures, wherein:

FIG. 1 is a flow chart of one embodiment of a method of makingmicrostructure.

FIG. 2 is a Scanning Electron Microscope (SEM) image of the drawn carbonnanotube film.

FIG. 3 is a Scanning Electron Microscope (SEM) image of a carbonnanotube structure consisting of a plurality of stacked drawn carbonnanotube precursor films.

FIG. 4 is a flow chart of a method of disposing the carbon nanotubelayer on the second substrate.

FIG. 5 is a structural schematic view of a patterned photoresistmicrostructure.

FIG. 6 is a structural schematic view of a patterned photoresistmicrostructure.

FIG. 7 is a flow chart of a lift-off method of makingmicro-nanostructure.

FIG. 8 is a flow chart of one embodiment of a method of makingmicro-nanostructure.

FIG. 9 is a structural schematic view of a photolithography mask plate.

FIG. 10 is a structural schematic view of a photolithography mask plate.

FIG. 11 is a flow chart of one embodiment of the method of makingmicro-nanostructure.

FIG. 12 is a flow chart of one embodiment of the method of makingmicro-nanostructure.

FIG. 13 is a structural schematic view of a photolithography mask plateused in the method of FIG. 11.

FIG. 14 is a flow chart of one embodiment of a method of making thelithographic mask of FIG. 13.

FIG. 15 is a flow chart of one embodiment of the method of makingmicro-nanostructure.

FIG. 16 is a structural schematic view of a photolithography mask plateused in the method of FIG. 15.

FIG. 17 is a flow chart of one embodiment of a method of making thelithographic mask of FIG. 16.

FIG. 18 is a flow chart of one embodiment of the method of makingmicro-nanostructure.

FIG. 19 is a structural schematic view of a photolithography mask plateused in the method of FIG. 18.

FIG. 20 is a flow chart of one embodiment of the method of making thelithographic mask of FIG. 19.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The connection can be such that the objects are permanently connected orreleasably connected. The term “substantially” is defined to beessentially conforming to the particular dimension, shape or other wordthat substantially modifies, such that the component need not be exact.The term “comprising” means “including, but not necessarily limited to”;it specifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like. It should be notedthat references to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

Referring to FIG. 1, an embodiment of a method of making microstructurescomprises:

S11, providing a first substrate 150, setting a photoresist layer 160 ona surface of the first substrate 150;

S12, covering a surface of the photoresist layer 160 with aphotolithography mask plate 100, wherein the photolithography mask plate100 includes a second substrate 110 and a composite layer 140 located ona surface of the second substrate 110;

S13, exposing the photoresist layer 160 by irradiating the photoresistlayer 160 through the photolithography mask plate 100 with ultravioletlight 180, wherein the ultraviolet light 180 reach the photoresist layer160 through the second substrate 110 and the composite layer 140;

S14, removing the photolithography mask plate 100 from the photoresistlayer 160, and developing the photoresist layer 160 to obtain apatterned photoresist microstructures 170.

In step S11, the first substrate 150 can be insulating materials such assilica or silicon nitride. The first substrate 150 can also beconductive materials such as gold, aluminum, nickel, chromium, orcopper. Also the first substrate 150 can be semiconductor materials suchas silicon, gallium nitride, or gallium arsenide. In one embodiment, thefirst substrate 150 is a silicon wafer.

The type of the photoresist layer 160 can be negative or positive. Thephotoresist layer 160 can be S9912 positive photoresist or SU8 negativephotoresist. The photoresist layer 160 can be directly applied to thesurface of the first substrate 150 by spin coating. The thickness of thephotoresist layer 160 can be in a range of about 50 nm to about 200 nm.When the thickness of the photoresist layer 160 is too thin, graphiccontrast after photolithography decreases. When the thickness of thephotoresist layer 160 is too thick, patterned photoresist can easilycreate slopes near the edge of the pattern. In one embodiment, thephotoresist layer 160 is S9912 positive photoresist, and the thicknessof the photoresist layer 160 is about 100 nm.

In step S12, the photolithography mask plate 100 provides a patternedmask. The photolithography mask plate 100 includes at least a secondsubstrate 110 and a composite layer 140 located on the surface of thesecond substrate 110. The composite layer 140 includes a carbon nanotubelayer 120 and a cover layer 130. The carbon nanotube layer 120 isdirectly located on the surface of the second substrate 110. The coverlayer 130 covers the carbon nanotube layer 120 so that the carbonnanotube layer 120 is sandwiched between the cover layer 130 and secondsubstrate 110. The cover layer 130 is continuously and directly attachedto a surface of the carbon nanotube layer 120. The cover layer 130 isbonded to the carbon nanotube layer 120 to form the composite layer 140.Due to portions of the cover layer 130 can extend through the holes ofthe carbon nanotube layer 120 to be in direct contact with the secondsubstrate 110, the cover layer 130 can fix the carbon nanotube layer 120on the second substrate 110.

The photolithography mask plate 100 covers the photoresist layer 160.The photolithography mask plate 100 is located on the surface of thephotoresist layer 160 away from the first substrate 150. In oneembodiment, the composite layer 140 is in direct contact with thesurface of the photoresist layer 160 away from the first substrate 150.The second substrate 110 is spaced from the photoresist layer 160. Inone embodiment, the second substrate 110 can be in direct contact withthe photoresist layer 160 so that the second substrate 110 sandwichedbetween the composite layer 140 and the photoresist layer 160. Thecomposite layer 140 is spaced from the photoresist layer 160. When thecomposite layer 140 is located on the surface of the photoresist layer160, the composite layer 140 is not completely in direct contact withthe surface of the photoresist layer 160, and there may be air gapsbetween partial surfaces of the composite layer 140 and surfaces of thephotoresist layer 160.

The second substrate 110 serves as a support. Materials of the secondsubstrate 110 can be rigid materials (e.g., p-type or n-type silicon,quartz, silicon with a silicon dioxide layer formed thereon, crystal,crystal with an oxide layer formed thereon), or flexible materials(e.g., plastic or resin). The second substrate 110 material can bepolyethylene terephthalate, polyethylene naphthalate two formic acidglycol ester (PEN), or polyimide. The second substrate 110 has a hightransmittance to UV light, for example more than 60%. In one embodiment,the second substrate 110 material is quartz.

The carbon nanotube layer 120 includes a plurality of carbon nanotubesparallel to the surface of the carbon nanotube layer 120. The pluralityof carbon nanotubes along an extending direction joined end to end byvan der Waals attraction 20 forces. The carbon nanotube layer 120 is afree-standing structure. The term “free-standing structure” includes thecarbon nanotube layer 120 that can sustain the weight of itself when itis hoisted by a portion thereof without any significant damage to itsstructural integrity. Thus, the carbon nanotube layer 120 can besuspended by two spaced supports (not shown). The plurality of carbonnanotubes can be single-walled carbon nanotubes, double-walled carbonnanotubes, or multi-walled carbon nanotubes. The length and diameter ofthe plurality of carbon nanotubes can be selected according to need. Thediameter of the single-walled carbon nanotubes can be from about 0.5nanometers to about 10 nanometers. The diameter of the double-walledcarbon nanotubes can be from about 1.0 nanometer to about 15 nanometers.The diameter of the multi-walled carbon nanotubes can be from about 1.5nanometers to about 50 nanometers. In one embodiment, the length of thecarbon nanotubes can be from about 200 micrometers to about 900micrometers.

The carbon nanotube layer 120 can include at least one carbon nanotubefilm, at least one carbon nanotube wire, or combination thereof. In oneembodiment, the carbon nanotube layer 120 can be pure carbon nanotubelayer. In one embodiment, the carbon nanotube layer 120 can include asingle carbon nanotube film or two or more carbon nanotube films stackedtogether. Thus, the thickness of the carbon nanotube layer 120 can becontrolled by the number of the stacked carbon nanotube films. In oneembodiment, the carbon nanotube layer 120 is formed by folding a singlecarbon nanotube wire. In one embodiment, the carbon nanotube layer 120can include a layer of parallel and spaced carbon nanotube wires. Also,the carbon nanotube layer 120 can include a plurality of carbon nanotubewires crossed or weaved together to form a carbon nanotube net. Thecarbon nanotube net defines a plurality of holes. The plurality of holesextend throughout the carbon nanotube layer 120 along the thicknessdirection of the layer. It is understood that any carbon nanotubestructure described can be used with all embodiments.

Referring to FIG. 2, in one embodiment, the carbon nanotube layer 120includes at least one drawn carbon nanotube film. A drawn carbonnanotube film can be drawn from a carbon nanotube array that is able tohave a film drawn therefrom. The drawn carbon nanotube film includes aplurality of successive and oriented carbon nanotubes joined end-to-endby van der Waals attraction forces therebetween. The drawn carbonnanotube film is a free-standing film. Each drawn carbon nanotube filmincludes a plurality of successively oriented carbon nanotube segmentsjoined end-to-end by van der Waals attraction forces therebetween. Eachcarbon nanotube segment includes a plurality of carbon nanotubesparallel to each other, and combined by van der Waals attraction forcestherebetween. As can be seen in FIG. 2, some variations can occur in thedrawn carbon nanotube film. The carbon nanotubes in the drawn carbonnanotube film are oriented along a preferred orientation. The drawncarbon nanotube film can be treated with an organic solvent to increasethe mechanical strength and toughness and reduce the coefficient offriction of the drawn carbon nanotube film. A thickness of the drawncarbon nanotube film can range from about 0.5 nanometers to about 100micrometers. The drawn carbon nanotube film defines a plurality of holesbetween adjacent carbon nanotubes.

Referring to FIG. 3, the carbon nanotube layer 120 can include at leasttwo stacked drawn carbon nanotube films. In other embodiments, thecarbon nanotube layer 120 can include two or more coplanar carbonnanotube films, and can include layers of coplanar carbon nanotubefilms. Additionally, when the carbon nanotubes in the carbon nanotubefilm are aligned along one preferred orientation (e.g., the drawn carbonnanotube film), an angle can exist between the orientation of carbonnanotubes in adjacent films, whether stacked or adjacent. Adjacentcarbon nanotube films can be combined by only the van der Waalsattraction forces therebetween. As can be seen in FIG. 3, an anglebetween the aligned directions of the carbon nanotubes in two adjacentcarbon nanotube films can range from about 0 degrees to about 90degrees. When the angle between the aligned directions of the carbonnanotubes in adjacent stacked drawn carbon nanotube films is larger than0 degrees, a plurality of holes is defined by the carbon nanotube layer120. In one embodiment, the carbon nanotube layer 120 is shown with thealigned directions of the carbon nanotubes between adjacent stackeddrawn carbon nanotube films at 90 degrees. Stacking the carbon nanotubefilms will also add to the structural integrity of the carbon nanotubelayer 120.

The carbon nanotube wire can be untwisted or twisted. Treating the drawncarbon nanotube film with a volatile organic solvent can form theuntwisted carbon nanotube wire. Specifically, the organic solvent isapplied to soak the entire surface of the drawn carbon nanotube film.During soaking, adjacent parallel carbon nanotubes in the drawn carbonnanotube film will bundle together, due to the surface tension of theorganic solvent as it volatilizes, and thus, the drawn carbon nanotubefilm will be shrunk into an untwisted carbon nanotube wire. Theuntwisted carbon nanotube wire includes a plurality of carbon nanotubessubstantially oriented along a same direction (i.e., a direction alongthe length of the untwisted carbon nanotube wire). The carbon nanotubesare substantially parallel to the axis of the untwisted carbon nanotubewire. More specifically, the untwisted carbon nanotube wire includes aplurality of successive carbon nanotube segments joined end to end byvan der Waals attraction forces therebetween. Each carbon nanotubesegment includes a plurality of carbon nanotubes substantially parallelto each other, and combined by van der Waals attraction forcestherebetween. The carbon nanotube segments can vary in width, thickness,uniformity, and shape. The length of the untwisted carbon nanotube wirecan be arbitrarily set as desired. A diameter of the untwisted carbonnanotube wire ranges from about 0.5 nanometers to about 100 micrometers.

The twisted carbon nanotube wire can be formed by twisting a drawncarbon nanotube film using a mechanical force at two opposite ends ofthe drawn carbon nanotube film in opposite directions. The twistedcarbon nanotube wire includes a plurality of carbon nanotubes helicallyoriented around an axial direction of the twisted carbon nanotube wire.More specifically, the twisted carbon nanotube wire includes a pluralityof successive carbon nanotube segments joined end to end by van derWaals attraction forces therebetween. Each carbon nanotube segmentincludes a plurality of carbon nanotubes parallel to each other, andcombined by van der Waals attraction forces therebetween. The length ofthe carbon nanotube wire can be set as desired. A diameter of thetwisted carbon nanotube wire can be from about 0.5 nanometers to about100 micrometers. Further, the twisted carbon nanotube wire can betreated with a volatile organic solvent after being twisted to bundlethe adjacent paralleled carbon nanotubes together. The specific surfacearea of the twisted carbon nanotube wire decreases while the density andstrength of the twisted carbon nanotube wire increases.

The carbon nanotube layer 120 can be located directly on the surface ofthe second substrate 110. As carbon nanotube layer 120 defines aplurality of holes, a partial surface of the second substrate 110 isexposed through the plurality of holes.

Furthermore, referring to FIG. 4, disposing the carbon nanotube layer120 on the second substrate 110 comprises solvent treating the secondsubstrate 110 with the carbon nanotube layer 120 thereon. Because thereis an air gap 112 between the carbon nanotube layer 120 and the surfaceof the second substrate 110, the solvent can exhaust air while allowingthe carbon nanotube layer 120 to be closely and firmly adhered on thesurface of the second substrate 110. The solvent can be water orvolatile organic solvent such as ethanol, methanol, acetone,dichloroethane, chloroform, or mixtures thereof. In one embodiment, theorganic solvent is ethanol.

The material of the cover layer 130 can be metal, metal oxide, metalnitride, metal carbide, metal sulfide, silicon oxide, silicon nitride,or silicon carbide. The metal can be gold, nickel, titanium, iron,aluminum, chromium, or alloy thereof. The metal oxide can be alumina,magnesium oxide, zinc oxide, or hafnium oxide. The material of the coverlayer 130 is not limited above and can be any material as long as thematerial can be deposited on the carbon nanotube layer 120 and have ahigh transmittance to UV light, for example more than 60%.

The cover layer 130 can be deposited on the surface of the carbonnanotube layer 120 by atomic layer deposition (ALD). The method ofdepositing the cover layer 130 can also be physical vapor deposition(PVD), chemical vapor deposition (CVD), magnetron sputtering, orspaying. The method of depositing the cover layer 130 is not limitedabove and can be any method as long as the cover layer 130 can becontinuously deposited on the carbon nanotube layer 120 surface and thestructure of the carbon nanotube layer 120 is not destroyed. Thethickness of the cover layer 130 is 5 nm-20 nm. If the thickness of thecover layer 130 is more than 20 nm, the transmittance to UV light of thecover layer 130 would be seriously reduced. In one embodiment, thematerial of the cover layer 130 is alumina, and the thickness of thecover layer 130 is 5 nm.

Furthermore, when the carbon nanotube layer 120 is a free-standingstructure, the composite layer 140 is also free-standing and can be usedalone as a lithographic pattern and the second substrate 110 is notoptional.

In step S13, when the ultraviolet light 180 irradiates on thephotolithography mask plate 100, due to the second substrate 110 and thecover layer 130 having high transmittance, the loss of the ultravioletlight 180 is negligible as the light 180 passes through the secondsubstrate 110 and the cover layer 130. As the carbon nanotubes iscapable of strongly absorbing the ultraviolet light, the ultravioletlight irradiated on the carbon nanotube structure is almost completelyabsorbed and the ultraviolet light irradiated at the holes betweencarbon nanotubes can pass directly through the carbon nanotube layer120. The photoresist layer 160 is exposed by irradiating the surface ofthe photoresist layer 160 through the photolithography mask plate 100with the ultraviolet light 180. The surface of the photoresist layer 160corresponding to the holes between the carbon nanotubes is exposed tothe ultraviolet light 180. The surface of the photoresist layer 160corresponding to the carbon nanotube structure is not exposed to theultraviolet light 180. The exposure time of the photoresist layer 160 isabout 2 s-7 s. In one embodiment, the exposure time of the photoresistlayer 160 is about 2 s.

In step S14, the photoresist layer 160 physically contacts thephotolithography mask plate 100, and the bonding force between thephotoresist layer 160 and the composite layer 140 is less than thebonding force between the composite layer 140 and the second substrate110. Thus, the photolithography mask plate 100 can be separated from thephotoresist layer 160 by applying a force to the second substrate 110,and the structure of the photolithography mask plate 100 would not bestrongly affected. After the photolithography mask plate 100 isseparated from the surface of the photoresist layer 160, the structureof the photolithography mask plate 100 remains intact. So thephotolithography mask plate 100 can be reused as a mask, and can be usedrepeatedly in steps S12-S13.

The photoresist layer 160 is subjected to a developing process byplacing the photoresist layer 160 in a developer for a period of time.The developer is a solution containing 0.4% NaOH and 1% NaCl solution.The developing time of the photoresist layer 160 is about 20 s. Thedeveloping time can be determined by the developer composition, theconcentration, and the like. The developer is not limited to above andcan be any solution as long as the photoresist layer 160 can bedeveloped. The developer can be a mixed solution of NaOH solution andNaCl solution. The mass content of NaOH in the mixed solution is about0.2%-1%, and the mass content of NaCl is about 0.5%-2%. The patternedphotoresist microstructures 170 are obtained after developing thephotoresist layer 160. The pattern of the patterned photoresistmicrostructures 170 is consistent with the pattern of the carbonnanotube layer 120. As can be seen in FIG. 5 and FIG. 6, the patternedphotoresist microstructures 170 include a plurality of ribs 171 and aplurality of micropores 172 between adjacent ribs 171, and themicropores 172 are holes or gaps. The width of the ribs 171 and thediameter of the micropores 172 are related to the diameter of the carbonnanotubes and the diameter of the holes in the carbon nanotube layer120. The size of the micropore is the diameter of the hole or width ofthe gap. The plurality of micropores 172 extend throughout the patternedphotoresist microstructures 170 along the thickness direction.

The thickness of the ribs 171 and the depths of the micropores 172 isconsistent with the thickness of the photoresist layer 160. The width ofeach ribs 171 is about 20 nm-200 nm, and the diameter of each microsporeis about 20 nm-300 nm.

Referring to FIG. 7, microstructures 152 formed by other non-photoresistmaterials can be further obtained according to the patterned photoresistmicrostructures 170. The microstructures 152 can be made by a lift-offmethod, etching, or a combination thereof The method for making themicrostructures 152 is not limit the aforementioned methods and can beany method as long as the microstructures 152 can be obtained. In oneembodiment, the microstructures 152 are made by the lift-off method.

The lift-off method of making the microstructures 152 includes followingsteps: step 1, depositing a preformed layer 190 on a surface of thepatterned photoresist microstructures 170 away from the first substrate150 and an exposed surface of the first substrate 150; step 2, immersingthe whole structure above in acetone, and removing the patternedphotoresist microstructures 170 to obtain the microstructures 152 on thefirst substrate 150.

In step 1, the preformed layer 190 material can be metal, insulatingmaterials, or semiconductor materials. The metal can be gold, silver,nickel, titanium, iron, aluminum, chromium, or alloy thereof. Theinsulating materials can be silicon oxide, silicon nitride. Thesemiconductor materials can be silicon, gallium nitride, galliumarsenide. The material of the preformed layer 190 is not limit above andcan be any material as long as the material does not react with acetone.The preformed layer 190 can be deposited by magnetron sputtering, vapordeposition, CVD method, or the like. The preformed layer 190 on thepatterned photoresist microstructures 170 is not continuous so that bothlateral sides of the patterned photoresist microstructures 170 are notcompletely covered by the preformed layer 190. Thus, the acetone can becontact and react with the patterned photoresist microstructures 170. Inone embodiment, the preformed layer 190 material is aluminum, and thepreformed layer 190 is made by vapor deposition method.

In step 2, as both lateral sides of the patterned photoresistmicrostructures 170 are not completely covered by the preformed layer190, the acetone can react with the photoresist to remove the patternedphotoresist microstructures 170. At the same time, portions of thepreformed layer 190 that are deposited on the patterned photoresistmicrostructures 170 surface can also be removed. The other portions ofthe preformed layer 190 that are deposited on the first substrate 150forms the microstructures 152. In one embodiment, the carbon nanotubelayer 120 includes two crossed drawn carbon nanotube films, and themicrostructures 152 is a vertical crossed strips structure. The width ofeach strip in the direction perpendicular to the extension direction isset to be 1, and the size of l is about 20 nm-200 nm, the width ofspacing between two adjacent strips is about 20 nm-300 nm. The thicknessof the microstructures 152 can be determined in accordance with thethickness of the preformed layer 190.

The microstructures 152 can also be formed by dry etching. The exposedsurface of the first substrate 150 is etched with the patternedphotoresist microstructures 170 as a mask. The dry etching can be plasmaetching or reactive ion etching (RIE). In one embodiment, the dryetching is performed by applying plasma energy on the entire or partialsurface of the first substrate 150 surface via a plasma device. Theplasma gas can be an inert gas and/or etching gases, such as argon (Ar),helium (He), chlorine (Cl₂), hydrogen (H₂), oxygen (O₂), fluorocarbon(CF₄), ammonia (NH₃), or air.

When etching the first substrate 150, the etching gas can react with thefirst substrate 150 and may not react with the patterned photoresistmicrostructures 170. The reaction rate between the etching gas and thepatterned photoresist microstructures 170 is much less than the reactionrate between the etching gas and the first substrate 150. The pattern ofthe microstructures 152 is substantially identical to the pattern of thepatterned photoresist microstructures 170.

Furthermore, method of making the microstructures 152 comprises removingthe patterned photoresist microstructures 170. The method of removingthe patterned photoresist microstructures 170 can be ultrasonic method,tearing method, oxidation method and so on. In one embodiment, thepatterned photoresist microstructures 170 are removed by ultrasonicmethod.

Referring to FIG. 8, an embodiment of a method of making microstructurescomprises:

S21, providing a first substrate 150, setting a photoresist layer 160 ona surface of the first substrate 150;

S22, covering a surface of the photoresist layer 160 with aphotolithography mask plate 200, wherein the photolithography mask plate200 includes at least two second substrates 110 and at least twocomposite layers 140, each composite layer 140 is located on one secondsubstrate 110 to form a photolithography mask plate unit;

S23, exposing the photoresist layer 160 by irradiating the photoresistlayer 160 through the photolithography mask plate 200 with theultraviolet light 180, wherein the ultraviolet light 180 reach thephotoresist layer 160 through the second substrate 110 and the compositelayer 140;

S24, removing the photolithography mask plate 200 from the photoresistlayer 160, and developing the photoresist layer 160 to obtain apatterned photoresist microstructures 170.

The method of making microstructures is similar to the above method ofmaking microstructures of FIG. 1 except that the photolithography maskplate 200 includes a plurality of second substrates and a plurality ofcomposite layers 140. Each second substrate and each composite layer 140locating on the second substrate 110 can be treated as aphotolithography mask plate unit. The photolithography mask plate 200includes a plurality of photolithography mask plate units. The pluralityof photolithography mask plate units are stacked, and the carbonnanotubes in the photolithography mask plate unit can be arranged inparallel in one direction, or intersected in a plurality of directions.

The mask pattern of the photolithography mask plate 200 can be adjustedby selecting photolithography mask plate units having differentarrangements of carbon nanotubes. If the mask pattern of thephotolithography mask plate 200 is a network pattern, the mask patterncan be obtained by directly selecting a photolithography mask unithaving intersected carbon nanotubes. Also the mask pattern can beobtained by selecting two photolithography mask units having parallelcarbon nanotubes, and the two photolithography mask units are stackedand the carbon nanotubes in the two units are arranged in differentdirections. As can be seen in FIG. 9, the angle a of the two units canbe selected as desired. As can be seen in FIG. 10, if the mask patternof the photolithography mask plate 200 includes a plurality of parallelstrips and an interval distance of each adjacent strips is 1, the maskpattern can be obtained by selecting two photolithography mask unitshaving parallel strips and the interval distance of each adjacent stripsis 2, wherein the two photolithography mask units are stacked and thestrips in the two photolithography mask units are in the same direction,and the strips of the two photolithography mask units alternates inpositions.

Referring to FIG. 11, an embodiment of a method of makingmicrostructures comprises:

S31, providing a first substrate 150, setting a photoresist layer 160 ona surface of the first substrate 150;

S32, covering a surface of the photoresist layer 160 with aphotolithography mask plate 300, wherein the photolithography mask plate300 includes a second substrates 110, a third substrate 109, and acarbon nanotube layer 120 sandwiched between the two substrates;

S33, exposing the photoresist layer 160 by irradiating the photoresistlayer 160 through the photolithography mask plate 300 with ultravioletlight 180, wherein the ultraviolet light 180 reach the photoresist layer160 through the photolithography mask plate 300;

S34, removing the photolithography mask plate 300 from the photoresistlayer 160 and developing the photoresist layer 160 to obtain a patternedphotoresist microstructures 170.

The method of making microstructures is similar to the above method ofmaking microstructures of FIG. 1 except that the photolithography maskplate 300 includes a second substrates 110, a third substrate 109, and acarbon nanotube layer 120 sandwiched between the two substrates. The useof the third substrate 109 is the same as that of the second substrate110, and the material of the third substrate 109 can be the same as thatof the second substrate 110. As the carbon nanotube layer 120 issandwiched between the third substrate 109 and the second substrate 110,the third substrate 109 and the second substrate 110 can fix and gripthe carbon nanotube layer 120. Due to the carbon nanotube layer 120 isfixed, it can not move on the plane and the direction perpendicular tothe plane. The method for making the photolithography mask plate 300 issimple, and the photolithography mask plate 300 having a fixed carbonnanotube layer is obtained without the step of depositing a cover layer.In one embodiment, the carbon nanotube layer 120 is a pure carbonnanotube layer and only comprises a plurality of carbon nanotubes.

Referring to FIG. 12, an embodiment of a method of makingmicrostructures comprises:

S41, providing a first substrate 150, setting a photoresist layer 160 ona surface of the first substrate 150;

S42, covering a surface of the photoresist layer 160 with aphotolithography mask plate 400, wherein the photolithography mask plate400 includes a second substrates 110, a first patterned chrome layer122, a carbon nanotube layer 120, and a cover layer 130;

S43, exposing the photoresist layer 160 by irradiating the photoresistlayer 160 through the photolithography mask plate 400 with ultravioletlight 180, wherein the ultraviolet light 180 reach the photoresist layer160 through the photolithography mask plate 400;

S44, removing the photolithography mask plate 400 from the photoresistlayer 160 and developing the photoresist layer 160 to obtain a patternedphotoresist microstructures 170.

The method of making microstructures is similar to the above method ofmaking microstructures of FIG. 1 except that the photolithography maskplate 400 includes a second substrates 110, a first patterned chromelayer 122, a carbon nanotube layer 120 and a cover layer 130. Thepattern of the first patterned chrome layer 122 coincides with thepattern of the carbon nanotube layer 120. The photolithography maskplate 400 can be used as a photolithography mask unit, and a pluralityof units are used in combination. Since the absorption rate of chromiumto the ultraviolet light is high, the photolithography mask plate 400has a better effect of absorbing ultraviolet light compared to a maskwith only carbon nanotubes. The microstructures obtained by thephotolithography mask plate 400 have higher accuracy compared to a maskwith only carbon nanotubes.

Referring to FIG. 13, the photolithography mask plate 400 abovecomprises: the second substrate 110, the first patterned chrome layer122, the carbon 10 nanotube layer 120, and the cover layer 130. Thefirst patterned chrome layer 122 is located on the surface of the secondsubstrate 110. The carbon nanotube layer 120 is located on a surface ofthe first patterned chrome layer 122 away from the second substrate 110.The pattern of the first patterned chrome layer 122 is the same with thepattern of the carbon nanotube layer 120. The cover layer 130 is locatedon the carbon nanotube layer 120 surface away from the second substrate110. The cover layer 130 is continuously and directly attached to thecarbon nanotube layer 120 surface. Because the cover layer 130 can coverthe entire carbon nanotube layer 120, the entire first patterned chromelayer 122, and a portion of the second substrate 110, the cover layer130 can fix the carbon nanotube layer 120 on the second substrate 110.

The photolithography mask plate 400 is similar to the photolithographymask plate 100 except that the photolithography mask plate 400 includesthe first patterned chrome layer 122 between the carbon nanotube layer120 and the second substrate 110. The pattern of the first patternedchrome layer 122 coincides with the pattern of the carbon nanotube layer120. Since the absorption rate of chromium to the ultraviolet light ishigh, the photolithography mask plate 400 has a better effect ofabsorbing ultraviolet light. The microstructures obtained by thephotolithography mask plate 400 have higher accuracy.

Referring to FIG. 14, an embodiment of a method of making thephotolithography mask plate 400 comprises:

S51, providing a second substrate 110, setting a chrome layer 121 on asurface of the second substrate 110;

S52, locating a carbon nanotube layer 120 on a surface of the chromelayer 121 to expose a partial surface of the chrome layer 121;

S53, etching the chrome layer 121 with the carbon nanotube layer 120 asa mask to obtain a first patterned chrome layer 122;

S54, depositing a cover layer 130 on a surface of the carbon nanotubelayer 120 away from the second substrate.

In step S51, the chrome layer 121 can be deposited by electron beamevaporation, ion beam sputtering, atomic layer deposition, magnetronsputtering, vapor deposition, chemical vapor deposition, etc. The chromelayer 121 is continuous and deposited on the second substrate 110. Thethickness of the chrome layer 121 is from about 10 nm to about 50 nm. Inone embodiment, the chrome layer 121 is deposited on the secondsubstrate 110 by vapor deposition, and the thickness of the chrome layer121 is 20 nm.

In step S52, the method of disposing the carbon nanotube layer 120 canbe the same with the method above. The method can make the carbonnanotube layer 120 closely and firmly adhered on the chrome layer 121surface. Partial surfaces of the chrome layer 121 corresponding to theholes of the carbon nanotube layer 120 are exposed.

In step S53, the etching method can be same with the method of etchingthe first substrate 150 above. The etching gases can be determined bythe material which is etched. And the etching gases can not react withthe carbon nanotube layer 120.

In step S54, the method of making the cover layer 130 is the same withthe method above. The cover layer 130 is directly attached to thesurface of the carbon nanotube layer 120 to form a continuous layerstructure, and cover the first patterned chrome layer 122 at the sametime. The carbon nanotube layer 120 is fixed on the second substrate 110by the cover layer 130.

Referring to FIG. 15, an embodiment of a method of makingmicrostructures comprises:

S61, providing a first substrate 150, setting a photoresist layer 160 ona surface of the first substrate 150;

S62, covering the surface of the photoresist layer 160 with aphotolithography mask plate 500, wherein the photolithography mask plate500 includes a second substrate 110, a first patterned chrome layer 122,a carbon nanotube layer 120, and a cover layer 130;

S63, exposing the photoresist layer 160 by irradiating the photoresistlayer 160 through the photolithography mask plate 500 with ultravioletlight 180, wherein the ultraviolet light 180 reach the photoresist layer160 through the photolithography mask plate 500;

S64, removing the photolithography mask plate 500 from the photoresistlayer 160, and developing the photoresist layer 160 to obtain apatterned photoresist microstructures 170.

The method of making microstructures is similar to the method of makingmicrostructures of FIG. 1 except that the first patterned chrome layer122 is located between the carbon nanotube layer 120 and the cover layer130. The pattern of the first patterned chrome layer 122 coincides withthe pattern of the carbon nanotube layer 120. Since the absorption rateof chromium and carbon nanotube to the ultraviolet light is high, themicrostructures obtained by the photolithography mask plate 500 havehigher accuracy.

Referring to FIG. 16, the photolithography mask plate 500 abovecomprises: the second substrate 110, the carbon nanotube layer 120, thefirst patterned chrome layer 122, and the cover layer 130. The carbonnanotube layer 120 is located on the surface of the second substrate110. The first patterned chrome layer 122 is located on the surface ofthe carbon nanotube layer 120 away from the second substrate 110. Thepattern of the first patterned chrome layer 122 is the same with thepattern of the carbon nanotube layer 120. The cover layer 130 covers onthe surface of the first patterned chrome layer 122 away from the secondsubstrate 110.

The photolithography mask plate 500 is similar to the photolithographymask plate 400 except that the first patterned chrome layer 122 islocated on the carbon nanotube layer 120 surface away from the secondsubstrate 110. The pattern of the first patterned chrome layer 122coincides with the pattern of the carbon nanotube layer 120. Themicrostructures obtained by the photolithography mask plate 500 havehigher accuracy.

Referring to FIG. 17, an embodiment of a method of making thephotolithography mask plate 500 comprises:

S71, providing a fourth substrate 101, setting a carbon nanotube layer120 on the fourth substrate 101;

S72, locating a chrome layer 121 on the surface of the carbon nanotubelayer 120 away from the fourth substrate 101, wherein the chrome layer121 includes a first patterned chrome layer 122 and a second patternedchrome layer 123, the first patterned chrome layer 122 is located on thesurface of carbon nanotubes of the carbon nanotube layer 120, and thesecond patterned chrome layer 123 is deposited on a surface of thefourth substrate 101 corresponding to holes of the carbon nanotube layer120;

S73, transferring the carbon nanotube layer 120 with the first patternedchrome layer 122 thereon from the surface of the fourth substrate 101 tothe surface of the second substrate 110, and the carbon nanotube layer120 being in contact with the surface of the second substrate 110;

S74, depositing a cover layer 130 on the surface of the first patternedchrome layer 122 away from the second substrate 110.

In step S72, when the thickness of the chrome layer 121 is smaller thanthe thickness of the carbon nanotube layer 120, the chrome layer 121 isa discontinuous structure. The chrome layer 121 is divided into thefirst patterned chrome layer 122 and the second patterned chrome layer123 away from each other. The first patterned chrome layer 122 islocated only on the surface of the carbon nanotubes. The secondpatterned chrome layer 123 is located on partial surfaces of the fourthsubstrate 101, and the partial surfaces corresponds to and is exposedfrom the holes of the carbon nanotube layer 120.

In step S73, since the chrome layer 121 is a discontinuous layeredstructure, the carbon nanotube layer 120 can be directly detached fromthe fourth substrate 101 surface. After the first patterned chrome layer122 and the carbon nanotube layer are transferred, the structure of thesecond patterned chrome layer 123 remains unchanged. The fourthsubstrate 101 and the second patterned chrome layer 123 can also be usedas a photolithography mask.

Referring to FIG. 18, an embodiment of a method of makingmicrostructures comprises:

S81, providing a first substrate 150, setting a photoresist layer 160 ona surface of the first substrate 150;

S82, covering a surface of the photoresist layer 160 with aphotolithography mask plate 600, wherein the photolithography mask plate500 includes a second substrate 110, a carbon nanotube compositestructure 141 and a cover layer 130;

S83, exposing the photoresist layer 160 by irradiating the photoresistlayer 160 through the photolithography mask plate 600 with ultravioletlight 180, wherein the ultraviolet light 180 reach the photoresist layer160 through the photolithography mask plate 600;

S84, removing the photolithography mask plate 600 from the photoresistlayer 160, and developing the photoresist layer 160 to obtain apatterned photoresist microstructures 170.

The method of making microstructures is similar to the method of makingmicrostructures of FIG. 1 except that the carbon nanotube compositestructure 141 is located on the surface of the second substrate 110 andcomprises a carbon nanotube layer 120, and a chrome layer 121 wraps thecarbon nanotube layer 120. The chrome layer 121 completely covers eachof carbon nanotubes in the carbon nanotube layer 120.

The features of the method of making microstructures includes thefollowing points. Since the carbon nanotubes and chromium have the highabsorption of ultraviolet light and the low transmittance to ultravioletlight, the transmittance to ultraviolet light of holes is very high,then it is easy to obtain patterned microstructures. The cover layer canfix the carbon nanotube layer on the second substrate to form a mask,and the mask is easy to disassemble and can be used repeatedly to cutcosts. Also the mask can be produced in a large scale.

Referring to FIG. 19, the photolithography mask plate 600 abovecomprises: the second substrate 110, the carbon nanotube compositestructure 141, and the cover layer 130. The carbon nanotube compositestructure 141 is located on the surface of the second substrate 110. Thecarbon nanotube composite structure 141 comprises a carbon nanotubelayer 120 and a chrome layer 121 wrapped the carbon nanotube layer 120.The cover layer 130 covers the surface of the carbon nanotube compositestructure 141 away from the second substrate 110.

The photolithography mask plate 600 is similar to the photolithographymask plate 500 except that the chrome layer 121 is wrapped only on thesurface of the carbon nanotubes in the carbon nanotube layer 120 and theholes between the carbon nanotubes are not covered by the chrome layer121. The microstructures obtained by the photolithography mask plate 600have a high precision.

Referring to FIG. 20, an embodiment of a method of making thephotolithography mask plate 600 comprises:

S91, providing the carbon nanotube composite structure 141, wherein thecarbon nanotube composite structure 141 comprises a carbon nanotubelayer 120 and a chrome layer 121 wraps the carbon nanotube layer 120;

S92, locating the carbon nanotube composite structure 141 on the surfaceof the second substrate 110 to expose partial surfaces of the secondsubstrate 110;

S93, depositing a cover layer 130 on the surface of the carbon nanotubecomposite structure 141 away from the second substrate 110.

The method of making the photolithography mask plate 600 is similar tothe method of making the photolithography mask plate 500 except that thechrome layer 121 wraps the entire surface of the carbon nanotubes in thecarbon nanotube layer 120. When the ultraviolet light passes through thephotolithography mask plate 600, the ultraviolet light can pass throughthe chrome layer twice. The photolithography mask plate 600 has a higherabsorption of UV light.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size, and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may comprisesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A method of making microstructures, comprising:setting a photoresist layer on a base; covering a surface of thephotoresist layer with a photolithography mask plate, wherein thephotolithography mask plate comprises: a substrate; a carbon nanotubelayer on the substrate; a patterned chrome layer on the carbon nanotubelayer so that the carbon nanotube layer is sandwiched between thepatterned chrome layer and the substrate, wherein a first pattern of thepatterned chrome layer is the same as a second pattern of the carbonnanotube layer; a cover layer on the patterned chrome layer; exposingthe photoresist layer to form an exposed photoresist layer byirradiating the photoresist layer through the photolithography maskplate with ultraviolet light; and developing the exposed photoresistlayer to obtain a patterned photoresist microstructures.
 2. The methodas claimed in claim 1, wherein a thickness of the photoresist layer isin a range of approximately 50 nm to approximately 200 nm.
 3. The methodas claimed in claim 1, wherein a transmittance of the substrate toultraviolet light is higher than 60%.
 4. The method as claimed in claim1, wherein the carbon nanotube layer is a free-standing structure andcomprises a plurality of carbon nanotubes joined end to end by van derWaals attraction forces along a length direction of the plurality ofcarbon nanotubes.
 5. The method as claimed in claim 1, wherein thecarbon nanotube layer comprises a carbon nanotube film, and the carbonnanotube film comprises a plurality of carbon nanotubes oriented at asubstantially same direction and successively joined end-to-end by vander Waals forces.
 6. The method as claimed in claim 4, wherein thecarbon nanotube layer comprises at least two stacked carbon nanotubefilms, and an angle between aligned directions of the carbon nanotubesin two adjacent carbon nanotube films is in a range from 0 degrees toabout 90 degrees.
 7. The method as claimed in claim 1, wherein the coverlayer comprise a material selected from the group consisting of gold,nickel, titanium, iron, aluminum, alumina, magnesium oxide, zinc oxide,hafnium oxide, and metal sulfide.
 8. The method as claimed in claim 1,wherein the cover layer is a continuous layer and located on a surfaceof the patterned chrome layer away from the substrate.
 9. The method asclaimed in claim 1, wherein the carbon nanotube layer is located betweenthe patterned chrome layer and the substrate.
 10. The method as claimedin claim 1, wherein the cover layer is directly attached to thepatterned chrome layer surface.
 11. The method as claimed in claim 1,wherein the substrate is in direct contact with the surface of thephotoresist layer.
 12. The method as claimed in claim 1, wherein thecover layer is in direct contact with the surface of the photoresistlayer.
 13. A method of making photolithography mask plate, comprising:setting a carbon nanotube layer on a substrate; depositing a chromelayer on the carbon nanotube layer, wherein the chrome layer comprises afirst patterned chrome layer and a second patterned chrome layer, thefirst patterned chrome layer is located on the carbon nanotube layer,and the second patterned chrome layer is deposited on the substratecorresponding to holes of the carbon nanotube layer; transferring thecarbon nanotube layer with the first patterned chrome layer thereon fromthe substrate to a base, and the carbon nanotube layer being in contactwith the base; and depositing a cover layer on the first patternedchrome layer.
 14. The method as claimed in claim 13, wherein the chromelayer is discontinuous and a thickness of the chrome layer is in a rangefrom approximately 10 nm to approximately 50 nm.
 15. The method asclaimed in claim 13, wherein after the carbon nanotube layer with thefirst patterned chrome layer thereon being transferred, the secondpatterned chrome layer is remained on the substrate to form another maskplate.